package com.jay.base.thread.book;

import sun.java2d.pipe.SpanShapeRenderer;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/**
 * Created by caoyuan7 on 2019/8/12.
 */
public class ThreadLocalDemo_Gc {
    static volatile ThreadLocal<SimpleDateFormat> tl = new ThreadLocal<SimpleDateFormat>(){
        protected void finalize() throws Throwable{
            System.out.println(this.toString() + " is gc");
        }
    };//加点技巧
    static volatile CountDownLatch cd = new CountDownLatch(10000);
    public static class ParseDate implements Runnable{
        int i = 0;
        public ParseDate(int i){
            this.i=i;
        }
        @Override
        public void run() {
            try{
                if(tl.get() == null){
                    tl.set(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"){
                              protected void finalize() throws Throwable{
                                  System.out.println(this.toString()+ " is gc");
                              }
                           });
                    System.out.println(Thread.currentThread().getId()+":create SimpleDateFormat");
                }
                Date t = tl.get().parse("2015-03-29 19:29:"+i%60);
            }catch (ParseException e){
                e.printStackTrace();
            }finally {
                cd.countDown();
            }
        }
    }
    public static void main(String args[]) throws InterruptedException{
        ExecutorService es = Executors.newFixedThreadPool(10);
        for (int i=0; i<10000;i++){
            es.execute(new ParseDate(i));
        }
        cd.await();
        System.out.println("mission complete!!");
        tl = null;
        System.gc();
        System.out.println("first GC complete!!");
        //在设置ThreadLocal的时候，会清除ThreadLocalMap中的无效对象
        tl = new ThreadLocal<SimpleDateFormat>();
        cd = new CountDownLatch(10000);
        for(int i = 0;i<10000;i++){
            es.execute(new ParseDate(i));
        }
        cd.await();
        Thread.sleep(1000);
        System.gc();
        System.out.println("second GC complete!!");
    }
}
